Norwich City manager Paul Lambert says striker James Vaughan will be out for "three or four" months after suffering a knee injury.
The 23-year-old hobbled out of Monday's 2-1 win over Sunderland, just 10 minutes after coming off the bench.
"He's going to be out for about 16 weeks or so, it's a blow for him and us," Lambert told BBC Radio Norfolk.
The Scot also confirmed midfielder Korey Smith will be out until next year with an ankle injury.
Meanwhile, defender Zak Whitbread will not recover from a hamstring problem in time to feature at Manchester United on Saturday.
"I'm absolutely gutted but I will work hard and make sure I come back stronger!"
Lambert added: "He had an operation the other day, his meniscus [cartilage in the knee] has been repaired.
"He was shattered the other night and you can understand why, because he battled really hard to come back and every injury he's getting seems to be a long one."
Injuries blighted Vaughan's time at Goodison Park, restricting him to only eight Premier League starts in six years.
He was forced to miss the start of the current campaign with a separate knee injury and has had three previous operations across both of the joints.